In the Vyprachticky U.S. Pat. No. 4,580,364, the many advantages derived from the use of constant force (also called "negator") springs in the design and operation of multiple-round cartridge magazines was fully explored. Then, in Dieringer application Ser. No. 052,232, now U.S. Pat. No. 4,765,081, one of us disclosed his solution to the curl problem inherent in such springs that causes the edges of the latter to dig into the cartridge casing, or bullets, or both, thus causing them to jam in certain style magazines where the tolerances are very tight. Finally, in our joint application Ser. No. 072,636, now U.S. Pat. No. 4,776,122, we jointly disclose yet another solution to the same problem having to do with curved as opposed to straight magazines. While both of these solutions to the spring curl problem work quite well and are currently in use, nevertheless, they involve certain compromises in terms of spring width, thickness, whether one or two such springs are used, and the location thereof relative to the cartridges, the sides and edges of the magazine. While all of these variables have been and are being accommodated, there remains a need for a simpler solution to the spring curl problem insofar as it relates to multiple-round cartridge magazines.
1. Field of the Invention
The present invention, therefore, relates to a novel and improved constant force anti-curl spring for use in multiple-round cartridge magazines.
2. Description of the Related Art
Transversely-slit and transversely-slotted springs are well known in the art as exemplified by the early Fuckley U.S. Pat. No. 345,767; Muffly's U.S. Pat. No. 2,087,354; Kuenzele's specialized spring forming the subject matter of his U.S. Pat. No. 3,533,431; and another old U.S. Pat. No. 630,503 issued to Greenfield. Some of the aforementioned spring structures comprise helical springs while others are circular or in some kind of leaf form. All, however, either have their side margins transversely slit alternately, first from one side and then the other or they have slots therein running transversely but not intersecting an edge. An even more highly specialized spring is the one shown in the Holick et al's U.S. Pat. No. 4,407,006 which, other than having its own peculiar chevron-shaped slot configuration, is not too much different than that of Greenfield except, of course, it is not helical and it is designed specifically for use as a semiconductor contact.
German Pat. No. 631 146 shows three versions of split tube springs having a circular cross section while Russian Pat. No. 274551 reveals a cylindrical spiral compression spring having a wave-like form. Another spring crimped transversely into a wave-like form is that forming the subject matter of Blomquist's U.S. Pat. No. 2,612,367, which spring is designed for use as a switch contact.
The closest prior art known to us is contained in the two U.S. patents to Lermont Nos. 2,609,192 and 3,007,239, both of which at FIG. 10 show a coil spring having two staggered rows of perforations 60 which are spaced apart gradually decreasing distances for the sole purpose of compensating for variations in the length of the moment arm of the force required to straighten or rewind the spirally-wound coil. None of the aforementioned references, however, teaches stress-relieving a constant force coil spring longitudinally for the purpose of lessening its transverse curl.